Power Plant Information
The reactors for Units 1, 2, and 6 were supplied by General Electric, those for Units 3 and 5 by Toshiba, and Unit 4 by Hitachi. All six reactors were designed by General Electric. Architectural design for General Electric's units was done by Ebasco. All construction was done by Kajima. Since September 2010, Unit 3 has been fueled by a small fraction (6%) of plutonium containing mixed-oxide (MOX) fuel, rather than the low enriched uranium (LEU) used in the other reactors. Units 1–5 were built with Mark I type (light bulb torus) containment structures. The Mark I containment structure was slightly increased in volume by Japanese engineers. Unit 6 has a Mark II type (over/under) containment structure.
Unit 1 is a 460 MW boiling water reactor (BWR-3) constructed in July 1967. It commenced commercial electrical production on March 26, 1971, and was initially scheduled for shutdown in early 2011. In February 2011, Japanese regulators granted an extension of ten years for the continued operation of the reactor. It was damaged during the 2011 Tōhoku earthquake and tsunami.
Unit 1 was designed for a peak ground acceleration of 0.18 g (1.74 m/s2) and a response spectrum based on the 1952 Kern County earthquake, but rated for 0.498 g. The design basis for Units 3 and 6 were 0.45 g (4.41 m/s2) and 0.46 g (4.48 m/s2) respectively. All units were inspected after the 1978 Miyagi earthquake when the ground acceleration was 0.125 g (1.22 m/s2) for 30 seconds, but no damage to the critical parts of the reactor was discovered. The design basis for tsunamis was 5.7 meters.
The reactor's emergency diesel generators and DC batteries, crucial components in helping keep the reactors cool in the event of a power loss, were located in the basements of the reactor turbine buildings. The reactor design plans provided by General Electric specified placing the generators and batteries in that location, but mid-level engineers working on the construction of the plant were concerned that this made the back up power systems vulnerable to flooding. TEPCO elected to strictly follow General Electric's design in the construction of the reactors.
Read more about this topic: Fukushima Daiichi Nuclear Power Plant
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